1. Field of the Invention
Exemplary embodiments of the present invention generally relate to an image forming apparatus and a process unit included in the image forming apparatus, and more particularly, to an image forming apparatus that effectively applies lubricant scraped from a solid lubricant onto an image carrier and removes residual toner from the image carrier, and a process unit that is included in the image forming apparatus.
2. Discussion of the Related Art
Recently, color image forming apparatuses using electrophotographic methods have come into widespread use. Digitalized images are now widely available, and as a result printed images are required to have higher image definitions. While research aimed at higher image resolution and gradient is being undertaken, research on the toner that makes visible an electrostatic latent image is directed toward making the toner particles more spherical in shape and with a smaller particle diameter, to form images having higher definition.
Examples of proposed methods for preparing toner having a substantially spherical shape and a small particle diameter include a method of using powdered toner having circular particles with a specific particle diameter distribution, a suspension polymerization method, a method in which a binder resin and a colorant are mixed in a solvent that does not blend with water and dissolved and dispersed in an aqueous medium under a dispersion stabilizer, a method in which a binder resin including a partially modified resin and a colorant are mixed in an organic solvent and dissolved and dispersed in an aqueous medium to cause a polyaddition reaction of the modified resin, and so forth. Such toner having a substantially spherical particle shape and a small particle diameter can enhance image quality and fluidity.
Since toner particles of small size and a spherical shape are reproduced faithfully, they are suitable for obtaining images having high definition. At the same time, however, such toner of small particle size and spherical shape can easily slip through a gap formed between a cleaning blade provided in a cleaning unit and a photoconductor and onto a surface of the photoconductor. Due to the spherical surface of the toner particle, the surface of the photoconductor cannot be easily cleaned, and the residual toner particles are scattered in the image forming apparatus to contaminate an image forming component such as a charging roller. As a result, a defective image having background fogging may be produced.
To eliminate the above-described circumstance an electrophotographic image forming method has been proposed, in which a cleaning member is included for cleaning or removing residual toner on a photoconductor by using an elastic rubber blade after transferring a toner image onto a recording medium, zinc stearate is incorporated in the toner in an amount ranging from approximately 0.01% to approximately 0.5% by toner weight, and the elastic rubber blade is substantially held on a contacting surface side of a cleaning blade on the photoconductor by a supporting member for fixing the elastic rubber blade on the cleaning member.
However, when the zinc stearate is added to the toner, while a high-density image area may receive a great amount of toner and a sufficient amount of zinc stearate may be supplied to the photoconductor, a less sufficient amount of toner may be supplied to a low-density image area and the amount of toner may not be sufficient. That is, a layer of the toner including the zinc stearate applied on the surface of the toner becomes uneven depending on a condition of an image to be developed, resulting in a defective image.
Further, a different technique has been proposed for a related-art image forming apparatus that includes a photoconductor that carries a latent image on a surface thereof, a charging unit that includes a charging member disposed in contact with the surface of the photoconductor or disposed opposite thereto in a vicinity of the surface thereof to charge the surface of the photoconductor, an optical writing unit that emits light and irradiates the surface of the photoconductor to form a latent image on the surface thereof, a developing unit that supplies toner onto the latent image to develop the latent image into a visible toner image, a transfer unit that produces a transfer electrical field between the photoconductor and a surface moving member contacting and moving on the surface of the photoconductor so as to transfer the toner image formed on the surface of the photoconductor onto a recording medium sandwiched between the photoconductor and the surface moving member or onto the surface moving member, and a cleaning unit that removes residual toner remaining on the surface of the photoconductor. The related-art image forming apparatus further includes an application unit including a brush roller that applies lubricant to the surface of the photoconductor to use a technique in which the brush roller slidably moves on a solid or molded lubricant to scrape lubricant from the solid lubricant and applies the scraped lubricant onto the surface of the photoconductor. The brush roller is disposed facing the solid or molded lubricant and supported by a pressing member such as a spring so as to bite a given amount into the solid or molded lubricant. When rotating, the brush roller slidably moves on the surface of the solid lubricant to scrape lubricant from the solid lubricant, and applies the scraped lubricant onto the surface of the photoconductor.
As a contact pressure force of the solid lubricant against the brush roller increases, the extent to which the brush roller bites into the solid lubricant also increases, thereby supplying a more sufficient amount of lubricant to the photoconductor and performing a more stable cleaning operation but also increasing the rotational load of the brush roller. As a result, a life of a drive unit or member of the brush roller may be shortened, costs of motors and power consumption may increase due to an increase of a motor torque, banding may be generated due to rotation vibration of the brush roller, and other disadvantages may be caused.